1. Field of the Invention
This invention relates to a process for preparing a purified rubbery polymer, more particularly to a process for removing in a high efficiency the catalyst residue contained in a rubbery polymer of ethylene and an .alpha.-olefin or of ethylene, an .alpha.-olefin and a non-conjugated diene (hereinafter referred to as EPDM) which has been obtained by a slurry polymerization method using a so-called Ziegler type catalyst.
2. Description of the Prior Art
The industrial process for the production of EPDM includes a solution polymerization method and a slurry polymerization method. The latter method is more advantageous in the following respects: (1) the viscosity of the reaction medium is low, and mass transfer and mixing are easy, and therefore, (2) it is possible to make the concentration of a polymer per unit amount of a solvent high. However, it also has following serious problems:
Since the polymer is deposited in the state that the catalyst is kept therein, it is difficult to remove the catalyst, and when the catalyst remains therein in a large amount, the remaining catalyst causes (a) coloring or aging of the polymer and (b) corrosion of metallic materials which are contacted with the polymer during the production process and the processing process.
Therefore, it has been desired to reduce the amount of the catalyst residue as much as possible in the slurry polymerization step.